What is a noindex tag, and how does it impact SEO?

A noindex tag is essentially an instruction you can provide to search engines about whether or not to include a particular webpage in their indexes and search results.

The noindex tag is a simple bit of code: <meta name="robots" content="noindex"> that gets added to the header section of a page's HTML. When search engine crawlers see this tag on a page, they'll obey the instructions and skip indexing and ranking that page in their search results.

There are a few main reasons you may want to use this tag for certain pages:

1) If there's content you don't want publicly available in search like private user profiles or staging development sites. The noindex tag hides this from being surfaced.

2) To control indexing for duplicate content versions by having the canonical version indexed while using noindex on the duplicates.

3) To temporarily remove certain lower-value pages from search results if needed.

The biggest impact is that pages with a noindex tag won't be indexed to be ranked and displayed in Google, Bing, etc. Any inbound links to that page also won't pass any link authority or equity around your site.

However, you have to be careful about overusing noindex tags haphazardly. They should only target low-value, unimportant pages you don't want to be indexed. Using it on important pages will limit your ability to get that content found and ranked in search.

So in summary - it's a tool to explicitly prevent indexing, but one that needs to be implemented very carefully and precisely as part of your overall SEO strategy.